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MALARIA
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MALARIA , an See also:Italian colloquial word (from See also:mala, See also:bad, and See also:aria, See also:air), introduced into See also:English medical literature by See also:Macculloch (1827) as a substitute for the more restricted terms "See also:marsh miasm" or "paludal See also:poison." It is generally applied to the definite unhealthy See also:condition of See also:body known by a variety of names, such as See also:ague, intermittent (and remittent) See also:fever, marsh fever, See also:jungle fever, See also: See also:Sleep may overtake the patient in the midst of the sweating stage, and he awakes, not without some feeling of what he has passed through, but on the whole well, with the temperature fallen almost or altogether to the normal, or it may be even below the normal; the pulse moderate and full; the spleen again of its See also:ordinary See also:size; the urine that is passed after the paroxysm deposits a thick See also:brick-red sediment of urates. The three stages together will probably have lasted six to twelve hours. The paroxysm is followed by a definite See also:interval in which there is not only no fever, but even a See also:fair degree of bodily comfort and fitness; this is the intermission of the fever. Another paroxysm begins at or near the same See also:hour next See also:day (quotidian ague), which results from a See also:double tertian infection, or the interval may be See also:forty-eight hours (tertian ague), or seventy-two hours (quartan ague). It is the See also:general See also:rule, with frequent exceptions, that the quotidian paroxysm comes on in the See also:morning, the tertian about See also:noon, and the quartan in the afternoon. Another rule is that the quartan has the longest cold stage, while its paroxysm is shortest as a whole; the quotidian has the shortest cold stage and a See also:long hot stage, while its paroxysm is longest as a whole. The point See also:common to the various forms of ague is that the paroxysm ceases about midnight or See also:early morning. Quotidian intermittent is on the whole more common than tertian in hot countries; elsewhere the tertian is the usual type, and quartan is only occasional. If the first paroxysm should not cease within the twenty-four hours, the fever is not reckoned ss an intermittent, but as a remittent. Remittent is a not unusual See also:form of the malarial See also:process in tropical and subtropical countries, and in some localities or in some seasons it is more common than intermittent. It may be said to arise out of that type of intermittent in which the cold stage is shortened while the hot stage tends to be prolonged. A certain See also:abatement or re-See also:mission of the fever takes See also:place, with or without sweating, but there is no true intermission or interval of See also:absolute apyrexia. The periodicity shows itself in the form of an exacerbation of the still continuing fever, and that exacerbation may take place twenty-four hours after the first onset, or the interval may be only See also:half that period, or it may be double. A fever that is to be remittent will usually declare it-self from the outset: it begins with chills, but without the shivering and shaking fit of the intermittent; the hot stage soon follows, presenting the same characters as the prolonged hot stage of the quotidian, with the frequent addition of bilious symptoms, and it may be even of See also:jaundice and of tenderness over the See also:stomach and See also:liver. Towards morning the fever abates; the pulse falls in frequency, but does not come down to the normal; headache and aching in the loins and limbs become less, but do not cease altogether; the body temperature falls, but does not See also:touch the level of apyrexia. The remission or abatement lasts generally throughout the morning; and about noon there is an exacerbation, seldom ushered in by chills, which continues till the early morning following, when it remits or abates as before. A patient with remittent may get well in a See also:week under treatment, but the fever may go on for several See also:weeks; the return to health is often announced by the fever assuming the intermittent type, or, in other words, by the remissions touching the level of absolute apyrexia. Remittent fevers (as well as intermittents) vary considerably in intensity; some cases are intense from the outset, or pernicious, with See also:aggravation of all the symptoms—leading to stupor, See also:delirium, collapse, intense jaundice, blood in the stools, blood and albumen in the urine, and, it may be, suppression of urine followed by See also:convulsions. The severe forms of intermittent are most See also:apt to occur in the very See also:young, or in the aged, or in debilitated persons generally. Milder cases of malarial fever are apt to become dangerous from the complications of See also:dysentery, See also:bronchitis or See also:pneumonia. Severe remittents (pernicious or bilious remittents) approximate to the type of yellow fever (q.v.), which is conventiohally limited to epidemic outbreaks in western longitudes and on the See also:west See also:coast of See also:Africa. Of the mortality due to malarial disease a small part only is referable to the See also:direct attack of intermittent, and chiefly to the fever in its pernicious form. Remittent fever is much more fatal in its direct attack. But probably the greater part of the enormous See also:total of deaths set down to malaria is due to the malarial cachexia. The dwellers in a malarious region like the Terai (at the See also:foot of the Himalayas) are miserable; listless and ugly, with large heads and particularly prominent ears, See also:flat noses, tumid bellies, slender limbs and sallow complexions; the See also:children are impregnated with malaria from their See also:birth, and their growth is attended with aberrations from the normal which practically amount to the disease of See also:rickets. The malarial cachexia that follows definite attacks of ague consists in a state of See also:ill-defined suffering, associated with a sallow skin, enlarged spleen and liver, and sometimes with See also:dropsy. See also:Causation.—From the See also:time of See also:Hippocrates onwards the malarial or periodical fevers have engaged the See also:attention of innumerable observers, who have suggested various theories of causation, and have sometimes anticipated—vaguely, indeed, but with surprising accuracy—the results of See also:modern See also:research; but the true nature of the disease remained in doubt until the closing years of the 19th See also:century. It has now been demonstrated by a See also:series of accurate investigations, contributed by many workers, that malaria is caused by a microscopic See also:parasite in the blood, into which it is introduced by the bites of certain See also:species of See also:mosquito. (See PARASITIC DISEASES and MosQuITOES.) The successive steps by which the See also:present position has been reached form an interesting See also:chapter in the See also:history of scientific progress. The first substantial See also:link in the actual History of See also:chain of See also:discovery was contributed in 188o by Discovery. Laveran, a See also:French See also:army surgeon serving in See also:Algeria. On the 6th of See also:November in that See also:year he plainly saw the living parasites under the See also:microscope in the blood of a malarial patient, and he shortly afterwards communicated his observations to the See also:Paris See also:Academic de Medecine. They were confirmed, but met with little See also:acceptance in the scientific See also:world, which was preoccupied with the claims of a subsequently discredited Bacillus malariae. In 1885 the Italian pathologists came See also:round to Laveran's views, and began to See also:work out the See also:life history of his parasites. The subject has a See also:special See also:interest for See also:Italy, which is devastated by malaria, and Italian See also:science has contributed materially to the See also:solution of the problem. The labours of Golgi, Marchiafava, Celli and others established the nature of the parasite and its behaviour in the blood; they proved the fact, guessed by Rasori so far back as 1846, that the periodical febrile paroxysm corresponds with the development of the organisms; and they showed that the different forms of malarial fever have their distinct parasites, and consequently fall into distinct See also:groups, defined on an etiological as well as a clinical basis—namely, the mild or See also:spring See also:group, which includes tertian and quartan ague, and the See also:malignant or " aestivo-autumnal " group, which includes a tertian or a semi-tertian and the true quotidian type. Three distinct parasites, corresponding with the tertian, quartan and malignant types of fever, have been described by Italian observers, and the See also:classification is generally accepted; intermediate types are ascribed to mixed and multiple infections. So far, however, only half the problem, and from the See also:practical point of view the less important half, had been solved. The origin of the parasite and its mode of introduction into the blood remained to be discovered. An old popular belief current in different countries, and derived from common observation, connected mosquitoes with malaria, and from time to time this theory found support in more scientific quarters on general grounds, but it lacked demonstration and attracted little attention. In 1894, however, See also:Sir See also:Patrick See also:Manson, arguing with greater precision by See also:analogy from his own discovery of the cause of See also:filariasis and the part played by mosquitoes, suggested that the malarial parasite had a similar intermediate See also:host outside the human body, and that a suctorial See also:insect, which would probably be found to be a particular mosquito, was required for its development. Following up this See also:line of investigation, See also:Major Ronald See also:Ross in 1895 found that if a mosquito sucked blood containing the parasites they soon began to throw out flagellae, which See also:broke away and became See also:free; and in 1897 he discovered See also:peculiar pigmented cells, which afterwards turned out to be the parasites of aestivo-autumnal malaria in an early stage of development, within the stomach-See also:wall of mosquitoes which had been fed on malarial blood. He further found that only mosquitoes of the genus Anopheles had these cells, and that they did not get them when fed on healthy blood. Then, turning his attention to the malaria of birds, he worked out the life-history of these cells within the body of the mosquito. " He saw that they increased in size, divided, and became full of filiform spores, then ruptured and poured out their multitudinous progeny into the body-cavity of their insect host. Finally, he saw the spores accumulate within the cells of the salivary glands, and discovered that they actually passed down the salivary ducts and along the grooved hypopharynx into the seat of puncture, thus causing infection in a fresh vertebrate host " (Sambon). To apply these discoveries to the malaria of See also:man was an obvious step. In working out the details the Italian school have again taken a prominent part. Thus we get a See also:complete scientific demonstration of the causation of malaria in three stages: (1) the discovery of the parasite by Laveran; (2) its life-history in the human host and connexion with the fever demonstrated by the Italian observers; (3) its life-history in the alternate host, and the See also:identification of the latter with a particular species of mosquito by Ross and Manson. The conclusions derived from the microscopical laboratory were confirmed by actual experiment. In 1898 Experiment. it was conclusively shown in Italy that if a mosquito of the Anopheles variety bites a See also:person suffering from malaria, and is kept long enough for the parasite to develop in the salivary gland, and is then allowed to bite a healthy person, the latter will in due time develop malaria. The See also:con- See also:verse proposition, that persons efficiently protected from mosquito bites See also:escape malaria, has been made the subject of several remarkable experiments. One of the most interesting was carried out in 1900 for the See also:London School of Tropical See also:Medicine by Dr Sambon and Dr See also:Low, who went to reside in one of the most malarious districts in the See also:Roman Campagna during the most dangerous See also:season. Together with Signor See also:Terzi and two Italian servants, they lived from the beginning of See also:July until the 19th of See also:October in a specially protected hut, erected near See also:Ostia. The See also:sole precaution taken was to confine themselves between sunset and sunrise to their mosquito- See also:proof dwelling. All escaped malaria, which was rife in the immediate neighbourhood. Mosquitoes caught by the experi- menters, and sent to London, produced malaria in persons who submitted themselves to the bites of these See also:insects at the London School of Tropical Medicine. Experiments in See also:pro- tection on a larger See also:scale, and under more ordinary conditions, have been carried out with equal success by See also:Professor Celli and other Italian authorities. The first of these was in 1899, and the subjects were the railwaymen employed on certain lines See also:running through highly malarious districts. Of 24 pro- tected persons, all escaped but four, and these had to be out at See also:night or otherwise neglected precautions; of 38 unprotected persons, all contracted malaria except two, who had apparently acquired See also:immunity. In 1900 further experiments gave still
better results. Of 52 protected persons on one line, all escaped
except two, who were careless; of 52 protected on another
line, all escaped; while of 51 unprotected persons, living in alternate houses, all suffered except seven. Out of a total of 207 persons protected in these railway experiments, 197 escaped. In two peasants' cottages in the Campagna, protected with See also:wire netting by Professor Celli, all the inmates—ro in number —escaped, while the neighbours suffered severely; and three out of four persons living in a third hut, from which See also:protection was removed owing to the indifference of the inmates, contracted malaria. In the malarious islet of Asinara a See also:pond of stagnant See also:water was treated with See also:petroleum and all windows were protected with See also:gauze. The result was that the houses were free from mosquitoes and no malaria occurred throughout the entire season, though there had been 40 cases in the previous year. Eight Red See also:Cross ambulances, each with a See also:doctor and attendant, were sent into the most malarious parts of the Campagna in 190o. By living in protected houses and wearing gloves and veils at night all the See also:staff escaped malaria except one or two attendants. These and other experiments, de-scribed by Dr Manson in the Practitioner for See also: The broad facts on which it is based are sufficiently accounted for by the habits of mosquitoes. For instance, the swampy See also:character of malarial areas is explained by their breeding in stagnant water; the effect of drainage, and the general immunity of high-lying, dry localities, by the lack of breeding facilities; the danger of the night air, by their nocturnal habits; the See also:comparative immunity of the upper storeys of houses, by the fact that they See also:fly low; the confinement of malaria to well-marked areas and the diminution of danger with distance, by their See also:habit of clinging to the breeding-grounds and not flying far. Similarly, the subsidence of malaria during cold See also:weather and its seasonal prevalence find an adequate explanation in the conditions governing insect life. At the same time it should be remembered that many points await elucidation, and it is unwise to assume conclusions in advance of the evidence. With regard to the parasites, which are the actual cause of malaria in man, an See also:account of them is given under the heading of PARASITIC DISEASES, and little need be said about parasites. them here. They belong to the group of See also:Protozoa, and, as already explained, have a double See also:cycle of existence: (r) a sexual cycle in the body of the mosquito, (2) an asexual cycle in the blood of human beings. They occupy and destroy the red corpuscles, converting the haemoglobin into melanin; they multiply in the blood by sporulation, and produce accessions of fever by the liberation of a toxin at the time of sporulation (Ross). The number in the blood in an acute attack is reckoned by Ross to be not less than 250 millions. A more general and practical interest attaches to the insects which See also:act as their intermediate hosts. These mosquitoes or gnats—the terms are synonymous—belong to the See also:family Culicidae and the genus Anopheles, which was first classified by Meigen in 1818. It has a wide See also:geographical See also:distribution, being found in See also:Europe (including England), See also:Asia See also:Minor, See also:Burma, Straits Settlements, See also:Java, See also:China, See also:Formosa, See also:Egypt; west, See also:south and Central Africa; See also:Australia, South See also:America, West Indies, See also:United States and See also:Canada, but is generally confined to See also:local centres in those countries. About fifty species are recognized at present. It is believed that all of them may serve as hosts of the parasite. The species best known in connexion with malaria are A. maculipennis (Europe and America), A. funestus and A. costales (Africa). In See also:colour Anopheles is usually brownish or slaty, but sometimes See also:buff, and the See also:thorax- frequently has a dark stripe on each See also:side. The wings in nearly all species have a dappled or speckled See also:appearance, owing to the occurrence of blotches on the front margin and to the arrangement of the scales covering the See also:veins in alternating See also:light and dark patches (See also:Austen). The genus with which Anopheles is most likely to be confounded is Culex, which is the commonest of all mosquitoes, has a world-wide distribution, and is generally a greedy blood-sucker. A distinctive feature is the position assumed in resting; Culex has a humpbacked attitude, while in Anopheles the See also:proboscis, See also:head and body are in a straight line, and in many species inclined at an See also:angle to the wall, the tail sticking outwards. In the See also:female of Culex the palpi are much shorter than the proboscis; in Anopheles they are of the same length. The wings in Culex have not the same dappled appearance. Anopheles is also a more slender insect, with a smaller head, narrower body and thinner legs. There are further See also:differences in the other stages of life. Mosquitoes go through four phases: (i) ovum, (2) larva, (3) nympha, (4) complete insect. The ova of Anopheles are tiny See also:black See also:rod-shaped See also:objects, which are deposited on the water of natural puddles, ponds, or slowly moving streams, by preference those which are well supplied with vegetation; they See also:float, singly or attached to other objects or clustered together in patterns. They can live in brackish and even in See also:sea water. The larva has no breathing-See also:tube, and floats horizontally at the surface, except when feeding; it does not frequent sewage or foul water. The ova of Culex, on the other See also:hand, are deposited in any stagnant water, including cesspools, drains, cisterns, or water collected in any See also:vessel; they float in See also:boat-shaped masses on the surface. The larva has a breathing-tube, and floats head downwards; when disturbed it wriggles to the bottom (See also:Christy). Some observers maintain that Anopheles does not " sing," like the common mosquito, and its bite is much less irritating. Only the See also:females suck blood; the act is believed to be necessary for fertilization and See also:reproduction. Anopheles rarely bites by day, and then only in dark places. In the daytime " the gorged females See also:rest motionless on the walls and ceilings of rooms, choosing always the darkest situations for this purpose " (Austen). In temperate climates the impregnated females hibernate during the See also:winter in houses, cellars, stables, the trunks of trees, &c., coming out to See also:lay their eggs in the spring. The four phases are passed in See also:thirty days in a favourable season, and consequently there are ordinarily four or five generations from See also:April to See also:September (Celli). The most important question raised by the mosquito-parasitic theory of malaria is that of prevention. This may be considered under two heads: (1) individual prophylaxis; (2) administrative prevention on a large scale. (i) In the first place, common sense suggests the avoidance, in malarious countries, of unhealthy situations, and particu- larly the neighbourhood of stagnant water. Among Pro- phylaxis. elements of unhealthiness is next to be reckoned the proximity of native villages, the inhabitants of which are infected. In the tropics " no See also:European See also:house should be located nearer to a native See also:village than half a mile " (Manson), and, since children are almost universally infected, " the presence of young natives in the house should be abso- lutely interdicted " (Manson). When unhealthy situations cannot be avoided, they may be rendered more healthy by destroying the breeding-grounds of mosquitoes in the neigh- bourhood. All puddles and collections of water should be filled in or drained; as a temporary expedient they may be treated with petroleum, which prevents the development of the larvae. When a place cannot be kept free from mos- quitoes the house may be protected, as in the experiments in Italy, by wire gauze at the doors and windows. The arrange- ment used for the entrance is a wire cage with double doors. Failing such protection mosquito curtains should be used. Mosquitoes in the house may be destroyed by the fumes of burning See also:sulphur or See also:tobacco See also:smoke. According to the experi- ments of Celli and Casagrandi, these are the most effective culicides; when used in sufficient quantity they kill mosquitoes in one See also:minute. The same authorities recommend a See also:powder, composed of larvicide (an See also:aniline substance), chrysanthemum See also:flowers, and See also:valerian See also:root, to be burnt in bedrooms. See also:Anointing the skin with strong-smelling substances is of little use in the open air, but more effective in the house; See also:turpentine appears to be the best. Exposure at night should be avoided. All these prophylactic See also:measures are directed against mosquitoes. There remains the question of protection against the parasite. Chills are recognized as predisposing both to See also:primary infection and to relapses, and malnutrition is also believed to increase susceptibility; both should therefore be avoided. Then a certain amount of immunity may be acquired by the systematic use of See also:quinine. Manson recommends five to ten grains once or twice a week; Ross recommends the same quantity every day before breakfast. There is some evidence that See also:arsenic has a prophylactic effect. An experiment made on the railway staff at Bovino, a highly malarious See also:district on the Adriatic, gave a striking result. The number of persons was 78, and they were divided into two equal groups of 39 each. One group was treated with arsenic, and of these 36 escaped altogether, while three had mild attacks; the remaining 39 who were not treated, all had fever. In a more extended experiment on 657 railway-men 402 escaped. This was in 1889; but in spite of the encouraging results the use of arsenic does not appear to have made any further progress. Experiments in immunizing by sero-therapeutic methods have not as yet met with success. (2) Much attention has been directed in scientific circles to the possibility of " stamping out " epidemic malaria by administrative measures. The problem is one Adminlsof See also:great practical importance, especially to the trative See also:British See also:Empire. There are no data for estimating Measures. the damage inflicted by malaria in the British colonies. It is, indeed, quite incalculable. In Italy the See also:annual mortality from this cause averages 15,000, which is estimated to represent two million cases of sickness and a consequent loss of several million francs. In British tropical possessions the See also:bill is incomparably heavier. There is not only the heavy See also:toll in life and health exacted from Europeans, but the virtual closing of enormous tracts of productive country which would otherwise afford See also:scope for British enterprise. The " deadly " climates, to which so much dread attaches, generally mean malaria, and the mastery of this disease would be See also:equivalent to the addition of vast and valuable areas to the empire. The problem, therefore, is eminently one for the statesman and See also:administrator. A solution may be sought in several directions, suggested by the facts already explained. The existence of the parasite is maintained by a vicious inter-See also:change between its alternate hosts, mosquitoes and man, each infecting the other. If the cycle be broken at any point the parasite must See also:die out, assuming that it has no other origin or mode of existence. The most effective step would obviously be the extermination of the Anopheles mosquito. A great See also:deal may be done towards this end by suppressing their breeding-places, which means the drying of the ground. It is a question for the engineer, and may require different methods in different circumstances. Put comprehensively, it involves the See also:control of the subsoil and surface See also:waters by drainage, the regulation of See also:rivers and floods, suitable See also:agriculture, the clearing of forests or jungles, which tend to increase the rainfall and keep the ground swampy. The See also:city of See also:Rome is an example of what can be done by drainage; situated in the midst of malaria, it is itself quite healthy. See also:Recent reports also show us how much may be done in infected districts. At See also:Ismailia malaria was reduced from 1551 cases in 1902 to 37 cases in 1905. The cost of operations amounted to an initial See also:expenditure of 6.25 francs, and an annual expenditure of about 2.3 francs per head of the See also:population. " The results are due to mosquito reduction together with cinchonization." The following' is a tabulated See also:list of the cases. The population of Ismailia is about 6000. Year . 1900 1901 1902' 1903 1904 1905 Cases of Malaria. 2250 1990 1548 214 90 37 2 Kiang and See also:Port Swettenham are contiguous towns in the Federated See also:Malay States, having a population of 4000 and a rainfall of roo in. a year. At Kiang the expenditure has been £3100, with an annual expenditure of £270, devoted to clearing and draining 332 acres. At Port Swettenham £7000, with an annual upkeep of £240, has been devoted to treating rro acres. In Hong-See also:Kong similar measures were carried out, with the result that the See also:hospital admissions for malaria diminished from 1294 in 1901, the year when operations were begun, to 419 in 1905. Kiang and Port Swettenham. A few other points may be noted. The pathological changes in malaria are due to the deposition of melanin and the detritus of red corpuscles and haemoglobin, and to the See also:congregation of parasites in certain sites (Ross). In chronic cases the eventual effects are See also:anaemia, melanosis, enlargement of the spleen and liver, and general cachexia. Apparently the parasites may remain quiescent in the blood for years and may cause relapses by fresh sporulation. Recent discoveries have done little or nothing for treatment. Quinine still remains the one specific. In serious cases it should not be given in solid form, but in solution by the stomach, rectum, or—better—hypodermically (Manson). According to Ross, it should be given promptly, in sufficient doses (up to 30 grains), and should be continued for months. Euquinine is by some preferred to quinine, but it is more expensive. Nucleogen and Aristochin have also been recommended instead of quinine. The nature of immunity is not known. Some persons are naturally absolutely immune (Celli), but this is rare; immunity is also some-times acquired by infection, but as a rule persons once infected are more predisposed than others. Races inhabiting malarious districts acquire a certain degree of resistance, no doubt through natural selection. Children are much more susceptible than adults. Malaria in the Lower Vertebrates.—Birds are subject to malaria, which is caused by blood parasites akin to those in man and having a similar life-history. Two species, affecting different kinds of birds, have been identified. Their alternate hosts are mosquitoes of the Culex genus. Oxen, See also:sheep, See also:dogs, monkeys, bats, and probably horses also suffer from similar parasitic diseases. In the See also:case of oxen the alternate host of the parasite is a special tick (See also: Additional information and CommentsThere are no comments yet for this article.
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